Field
The described technology generally relates to an organic light-emitting diode display.
Description of the Related Technology
An organic light-emitting diode (OLED) includes two electrodes and an organic light emitting layer positioned therebetween. Electrons injected from a cathode electrode and holes injected from an anode electrode are bonded to each other in the organic light emitting layer to form excitons. Light is emitted when the excitons discharge energy.
An OLED display includes a matrix of pixels, thin film transistors and capacitors for driving the OLED formed in each pixel.
An OLED display can include one of two driving methods: an analog driving method in which current is changed to generate gray levels and a digital driving method in which emitting time is controlled by a switching operation of a driving transistor to generate gray levels. For example, in the digital driving method, it is crucial for a driving transistor inside a pixel to stably implement as many sub frames as possible in one frame. Accordingly, in order to minimize the load of a data line, data line resistance should be decreased and an voltage (IR) drop should be minimized.
In the case of the digital driving method, since the driving voltage is directly applied to the OLED to determine luminance, the influence of the IR drop is strong, such that a luminance deviation due to a current deviation is greatly increased and thus, long range uniformity (LRU) of the OLED display panel decreases.
That is, in the pixel close to an external driving voltage supplier, since the IR drop amount is small, the driving voltage applied to the OLED is high compared to the pixel far from the external driving voltage supplier. Accordingly, the amount of the driving current is relatively increased in the pixel close to the external driving voltage supplier and the temperature at the close pixel increases compared to the far pixel. As described above, due to the increase of the temperature of the pixel close to the external driving voltage supplier as well as the increase of the driving voltage, a driving current deviation is generated between the close pixel and the far pixel, such that a luminance deviation is generated.
Also, the luminance of the close pixel is very bright, such that the lifespan of the close pixel close can be shortened.
The above information disclosed in this Background section is only to enhance the understanding of the background of the disclosure and therefore it can contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.